Ortak Dersler Bölümü
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Article Citation - WoS: 1Citation - Scopus: 1Effect of Estimation Under Nonnormality on the Phase Ii Performance of Linear Profile Monitoring Approaches(Wiley, 2019) Aytacoglu, Burcu; Bayrak, Ozlem TurkerThe number of studies about control charts proposed to monitor profiles, where the quality of a process/product is expressed as function of response and explanatory variable(s), has been increasing in recent years. However, most authors assume that the in-control parameter values are known in phase II analysis and the error terms are normally distributed. These assumptions are rarely satisfied in practice. In this study, the performance of EWMA-R, EWMA-3, and EWMA-3(d(2)) methods for monitoring simple linear profiles is examined via simulation where the in-control parameters are estimated and innovations have a Student's t distribution or gamma distribution. Instead of the average run length (ARL) and the standard deviation of run length, we used average and standard deviation of the ARL as performance measures in order to capture the sampling variation among different practitioners. It is seen that the estimation effect becomes more severe when the number of phase I profiles used in estimation decreases, as expected, and as the distribution deviates from normality to a greater extent. Besides, although the average ARL values get closer to the desired values as the amount of phase I data increases, their standard deviations remain far away from the acceptable level indicating a high practitioner-to-practitioner variability.Article Citation - WoS: 3Citation - Scopus: 3Temperature and Excitation Intensity Tuned Photoluminescence in Ga0.75in0.25se Crystals(Elsevier Science Bv, 2013) Isik, M.; Guler, I.; Gasanly, N. M.Photoluminescence (PL) spectra of Ga0.75In0.25Se layered single crystals have been studied in the wavelength range of 580-670 nm and temperature range of 7-59 K. Two PL emission bands centered at 613 nm (2.02 eV, A-band) and 623 nm (1.99 eV, B-band) were revealed at T = 7K. The excitation laser intensity dependence of the emission bands have been studied in the 0.06-1.40 W cm(-2) range. Radiative transitions from shallow donor levels located at E-A = 0.11 and E-B = 0.15 eV below the bottom of conduction band to single shallow acceptor level located at 0.01 eV above the valence band are suggested to be responsible for the observed A- and B-bands. A simple model was proposed to interpret the recombination processes in Ga0.75In0.25Se single crystals. (c) 2012 Elsevier B.V. All rights reserved.Article Fosfonat-substitüye Bodıpy Tasarımı, Sentezi ve Spektroskopik/fotofiziksel Karakterizasyonu(2020) Taşgın, Dilek IşıkBODIPY bileşikleri floresan sensör veya boya olarak geniş kullanım alanına sahip olması ve üstün fotofiziksel özelliklerinden dolayı multidisipliner alanlardaki bilim insanlarının ilgisini çekmeye devam etmektedir. Bu çalışmada, yeni bir fosfonat-substitüye BODIPY boyası, pirol ve aldehitten kondenzasyon-yükseltgenme-kompleksleşme metodu kullanılarak sentezlenmiştir. Sentezlenen BODIPY bileşiğinin yapısı ve fotofiziksel özellikleri 1 H NMR, 13C NMR, 31P NMR, 19F NMR, UV-Vis absorpsiyon ve floresans spektroskopi teknikleriyle tanımlanmıştır.Conference Object Estimation of AR(1) Model Having Generalized Logistic Disturbances(2020) Akkaya, Ayşen; Türker Bayrak, ÖzlemNon-normality is becoming a common feature in real life applications. Using non-normal disturbances in autoregressive models induces non-linearity in the likelihood equations so that maximum likelihood estimators cannot be derived analytically. Thus, modified maximum likelihood estimation (MMLE) technique is introduced in literature to overcome this difficulty. However, this method assumes the shape parameter to be known which is not realistic in real life. Recently, for unknown shape parameter case, adaptive modified maximum likelihood estimation (AMMLE) method that combines MMLE with Huber estimation method is suggested in literature. In this study, we adopt AMMLE method to AR(1) model where the disturbances are Generalized Logistic distributed. Although Huber M-estimation is not applicable to skew distributions, the AMMLE method extends Huber type work to skew distributions. We derive the estimators and evaluate their performance in terms of efficiArticle Citation - WoS: 9Optical Analysis of Tlins2xse2(1-X) Mixed Crystals(Amer inst Physics, 2014) Guler, I.The ellipsometry measurements were carried out on TlInS2xSe2(1-x) mixed crystals in the spectral range of 1.5-6.0 eV at room temperature. The refractive index, extinction coefficient, real and imaginary parts of dielectric function were found as a result of ellipsometric measurements. The energies of interband transitions (critical point energies) of the TlInS2xSe2(1-x) mixed crystals were obtained by means of the second derivative of the real and imaginary parts of dielectric function. The variation of the critical point energies with the isomorphic anion substitution that is sulfur for selenium atoms was established. (C) 2014 AIP Publishing LLC.Article Citation - WoS: 2Citation - Scopus: 2Thermoluminescence Characterization of (Ga2se3)0.25 - (Ga2s3)0.75 Single Crystal Compounds(Elsevier Sci Ltd, 2020) Guler, I; Gasanly, N. M.; Isik, M.Ga2Se3 and Ga2S3 compounds take attention due to their potential applications in photovoltaics. Defects and impurities may affect the quality of optoelectronic devices. Therefore, it is worthwhile to determine the parameters (activation energy, order of kinetics, frequency factor) of traps associated with the defects and/or impurities. The aim of the present paper is to investigate the trapping parameters of (Ga2Se3)(0.25) - (Ga2S3)(0.75) single crystal which is one of the member of (Ga2Se3)(x) - (Ga2S3)(1-x) mixed crystals. For this purpose, thermoluminescence (TL) experiments were performed on (Ga2Se3)(0.25) - (Ga2S3)(0.75) single crystals in the 10-300 K region. TL spectra were also recorded using various heating rates in between 0.2 and 1.0 K/s and stopping temperatures from 30 to 60 K to get the detailed information about the characteristics of the trapping parameters. TL glow curves exhibited the overlapped peaks. The stopping temperature experimental data indicated that traps present quasi-continuous distribution within the band gap. Initial rise method analyses were applied to get the activation energies of quasi-continuously distributed revealed traps. Thermal activation energies of distributed traps were found as increasing from 108 to 246 meV as stopping temperature was increased from 30 to 60 K. The structural characteristics (lattice constants and atomic compositions of constituent elements) of used compound were also reported in the present study.Article Analysis of the Specific Heat and the Free Energy of [N(Ch 3 ) 4 ] 2 Znbr 4 Close to the Ferro-Paraelastic Phase Transition(Taylor&Francis LTD, 2019) Kiracı, AliA power-law formula deduced from the Ising model was used to analyze the temperature dependence of the specific heat C p and the Gibbs free energy G of [N(CH 3 ) 4 ] 2 ZnBr 4 compound in the vicinity of the phase transition temperature of T C = 287.2 K. Obtained values of the critical exponents α from the Gibbs free energy were consistent with that predicted from 2-d potts model (α = 0.3), while obtained values of α from the specific heat in both ferroelastic and paraelastic phases were consistent with that predicted from the mean field theory (α = 0) in the vicinity of the phase transition temperature. This is an indication of that [N(CH 3 ) 4 ] 2 ZnBr 4 compound undergoes a second order type phase transition. Also, the enthalpy (H) and the entropy (S) of this crystal were calculated in terms of the extracted values of the critical exponent in both ferroelastic and paraelastic phases.Conference Object Citation - WoS: 2Citation - Scopus: 1Inter-Laboratory Comparison Scheme for Fuel Sector, Labkar in Turkey(Springer, 2009) Bayrak, Ozlem Turker; Okandan, Ender; Uckardes, HaleFuel sector is one of the powerful sectors in Turkish industry. The implementation of a new law for regulating the fuel sector had enforced the quality control of fuels sold to public. This resulted in several accredited fuel-testing laboratories to emerge. Thus, a scheme to evaluate their proficiency in measurements became an important requirement. The inter-laboratory comparison scheme LABKAR for gasoline, diesel oil, LPG, lubricating oil and biodiesel samples have evolved to fulfill this need. In this paper, LABKAR is introduced; the results obtained from the program are analyzed and discussed. The kernel densities of the participants' results show that the use of robust mean as a consensus value is appropriate for fuel samples. Although the number of rounds is not enough to derive strict conclusions, it is seen that the performance of the scheme based on the standard deviations and coefficient of variations is improving in each round. It has been observed that the number of laboratories receiving "action" or "warning" is decreasing, which indicates that they are benefiting from the scheme.Article Citation - WoS: 2Citation - Scopus: 3A Phenomenological Study on Ferroelectric Β-Glycine(Taylor & Francis Ltd, 2021) Kiraci, A.The anomalous behavior of the specific heat for beta-glycine was analyzed in terms of the compressible Ising model approximately 5 K below and above the ferrelectric-paraelectric phase transition temperature of T-C =252 K. The obtained value of the critical exponent alpha =0.12 in the ferroelectric phase (T < TC) was consistent with that predicted from the 3-d Ising model (alpha =0.13), while the obtained value of alpha =0.32 in the paraelectric phase (T > TC) was consistent with that predicted from the 2-d potts model (alpha =0.30). Some thermodynamic quantities such as the internal energy, the entropy and the free energy of beta-glycine were then predicted in terms of these extracted values of the critical exponents close to the phase transition temperature of TC. Our calculated values of the thermodynamic quantities are in good agreement with the observed data.Article Handan Romanında Batılılaşmış Kadın Karşısında batılılaş(Ama)mış Erkekler(2019) Atabağsoy, NaimTürk edebiyatında roman türünde eser veren yazarların Batılılaşma meselesine yoğun olarak ilgigösterdiği görülür. Bu aynı zamanda, özellikle 19. yüzyılın ikinci yarısı ve 20. yüzyılın başlarındatoplumsal olarak Batılılaşmaya yönelik mevcut eğilimin bir tezahürüdür. Toplumdaki bu yenileşmesürecinde kadının konumu da elbette sorgulanmış ve bu konu edebiyatta, çoğunlukla romanlararacılığıyla karşımıza çıkmıştır. Bu anlamda çalışma, kadın hareketlerindeki görünürlüğüyle debilinen Halide Edip Adıvar’ın mektuplaşmalar biçiminde kaleme alınmış 1912 tarihli romanıHandan’ı odağına almaktadır. Romanın merkezindeki karakter olan Handan’ın kendisinibirbirinden farklı şekillerde arzulayan ve Batılılaşmış görünen erkek karakterlerle sorunlu ilişkisi,modernleşme sürecinde kadının toplumdaki konumunu da sorgulamaya iter. Romanda Nâzım,Hüsnü Paşa ve Refik Cemal karakterleri, bu süreci Batı’yı yüzeysel biçimde taklit ederek tecrübe edenerkek karakterlerdir. Bu erkek karakterler, toplumdaki yeni tip erkeği farklı şekillerde temsil ederkenbuna paralel gelişen yeni kadın tipini çelişkili biçimde özümseyememektedirler. Handan, toplumsalmeselelerde fikirleri olan iyi eğitimli bir kadındır. O, geleneksel çizgideki hemcinslerine kıyaslaerkeklerle daha rahat iletişim kurar, erkeklerin de bulunduğu meclislerde serbestçe görüşleriniaçıklar, üstelik onlarla tartışmalara girmekten geri durmaz. Handan bu yönleriyle Nâzım’da, HüsnüPaşa’da ve Refik Cemal’de belirgin bir çekince uyandırır. Çalışma Handan’ın bu üç erkekle ilişkisine,erkeklerin bu yeni toplumsal süreçte kadınlar karşısındaki çelişkili tutumuna ve Handan’ın gelenekkarşısındaki konumlanışına eğilmektedir.Book Part Tarihten Günümüze Taşınanlar(Etimesgut Belediye Başkanlığı Kültür Yayınları, 2019) Atıcı, TüzelArticle Citation - WoS: 3Citation - Scopus: 4Development of a Selective Wet-Chemical Etchant for Precise 3d Sculpting of Silicon Enabled by Infrared Non-Linear Laser Modification(Elsevier Sci Ltd, 2024) Borra, Mona Zolfaghari; Radfar, Behrad; Nasser, Hisham; Colakoglu, Tahir; Tokel, Onur; Turnali, Ahmet; Bek, AlpanRecently-demonstrated high-quality three-dimensional (3D) subsurface laser processing inside crystalline silicon (c-Si) wafers opens a door to a wide range of novel applications in multidisciplinary research areas. Using this technique, novel maskless micro-pillars with precise control on the surface reflection and coverage are successfully fabricated by etching the laser-processed region of the c-Si wafer. To achieve this, a particular selective wet chemical etching is developed to follow subsurface laser processing of c-Si to reveal the desired 3D structures with smooth surfaces. Here, we report the development of a novel chromium-free chemical etching recipe based on copper nitrate, which yields substantially smooth surfaces at a high etch rate and selectivity on the both laserprocessed Si surface and subsurface, i.e., without significant etching of the unmodified Si. Our results show that the etch rate and surface morphology are interrelated and strongly influenced by the composition of the adopted etching solution. After an extensive compositional study performed at room temperature, we identify an etchant with a selectivity of over 1600 times for laser-modified Si with respect to unmodified Si. We also support our findings using density functional theory calculations of HF and Cu adsorption energies, indicating significant diversity on the c-Si and laser-modified surfaces.Article Citation - WoS: 4Citation - Scopus: 4Characterization of N Rich-Silicon Nitride Thin Films Deposited by Pecvd(Electrochemical Soc inc, 2023) Guler, I.Silicon nitride thin films are very important for their possible use in semiconductor industry and electronic applications. Changing the deposition parameters, silicon nitrides which have many varying optical properties can be produced. In this work, silicon nitride (SiNx) thin films were deposited on silicon substrates using Plasma enhanced chemical vapor deposition (PECVD) technique. The silane (SiH4) and ammonia (NH3) were used as reactant gases. Using these reactant gases, nitrogen (N) rich SiNx films were obtained. In order to get information about absorption and bond types in the films, films were analyzed by the help of Fourier transform infrared spectroscopy (FTIR) was performed. The refractive index, extinction coefficient and band gap energy of the films were changed from 1.86, 0 and 5.38 eV to 2.05, 0.0048 and 4.26 eV, respectively. Using the refractive index, composition of the films were estimated that is [N]/[Si] ratio of the films varied from 1.38 to 1.62. For possible applications of the SiNx films, learning the origin of the light-emission of the films is very important so the photoluminescence (PL) measurements were also used to see the luminescent of the SiNx films which is related to the electronic transitions between the K-center level and the conduction band tail states.Book Türk Romanında Gayrimüslime Bakış (1900-1960)(Libra Yayınevi, 2018) Atabağsoy, NaimTürk romanında 1900–1960 yılları arasında yayımlanan eserlerden seçilen örnekler yoluyla gayrimüslim karakterlerin ele alınışına odaklanan bu çalışma, aynı süreçte gayrimüslimler bağlamında öne çıkan siyasi, toplumsal ve ekonomik gelişmeleri de irdelemekte, böylelikle edebî ürünlerin tarihsel bağlam içerisinde anlamlandırılmasını amaçlamaktadır. Osmanlı İmparatorluğu’nun birçok alanda avantajlı konumda gösterilen gayrimüslim tebaası, Cumhuriyet’in ilan edilmesiyle birlikte azınlık statüsüne yerleştirilirken bu statünün hukuki zeminini oluşturan Lozan Antlaşması bu noktada dikkat çekici hâle gelir. Bu bakımdan bu çalışma, Antlaşma’nın imzalandığı 1923 yılını teorik olarak merkezine almaktadır. Çalışma, 1923 yılını hazırlayan süreçte ve Cumhuriyet dönemindeki iktidar değişimleriyle geçirilen 1960’a kadarki evrelerde öne çıkan gelişmeleri ve gayrimüslimler bakımından kırılma noktası niteliği taşıyan toplumsal olayları göz önüne alarak roman türündeki eserlerin, içerdiği gayrimüslim karakterler ve gayrimüslim kimliğine ilişkin söylemler üzerinden bu dönüşüm süreçlerinde nasıl reaksiyonlar gösterdiğini ortaya koyma gayreti taşımaktadır.Article Citation - WoS: 7Citation - Scopus: 7Exploring the Linear and Nonlinear Optical Behavior of (Tlins2)0.75 Insights From Ellipsometry Measurements(Elsevier, 2023) Guler, I.; Gasanly, N.; Isik, M.The search for layered structured new semiconductor materials with remarkable optical properties has become a driving force, especially for materials science. Tl2In2S3Se [(TlInS2)0.75(TlInSe2)0.25], a fascinating compound, holds great promise for advanced photonic and optoelectronic applications. In the present study, the linear and nonlinear optical properties of Tl2In2S3Se layered single crystals were studied by ellipsometry measurements. The variation of refractive index, extinction coefficient, absorption coefficient and skin depth with energy were investigated. Applying the derivative analysis technique to the absorption spectrum, indirect bandgap was found as 2.19 eV. The refractive index data was analyzed considering single-effective-oscillator model. The lattice dielectric constant, plasma frequency, carrier density to the effective mass ratio and zero-frequency refractive index were found. Moreover, the change in optical conductivity with energy yielded to determine the direct bandgap as 2.40 eV. The optical parameters of nonlinear refractive index, first-and third-order nonlinear susceptibilities were also reported.Article Bibliyografik Künye Karekodu Oluşturma Etkinliğine Yönelik Öğrenci, Öğretmen ve Okul Kütüphanecisi Görüşleri(2019) Çetin, Nihal Menzi; Akkoyunlu, BuketBilgi ve iletişim teknolojileri bilgiye erişme, bilgiyi paylaşma, iletme, bilgi ile iletişim kurma,yazma ve sunum yapma gibi işlemleri yerine getiren çeşitli araçlar sunmaktadır. Karekodlarmobil araçlarda kullanılan ve bilgiye erişimi hızlandıran araçlardan biridir. İlgi çekici vekullanımı kolay bir araç olarak karekodlardan eğitim ortamında faydalanılmakta ve olumlusonuçlar elde edilmektedir. Çeşitli araçları kullanarak bilgi becerilerini kazandırmayıamaçlayan ‘bilimsel iletişim öğretim programı’ ortaokul altıncı sınıf öğrencilerine yönelikgeliştirilmiş ve uygulanmıştır. Bu çalışmada bilimsel iletişim öğretim programında yer alanetkinliklerden biri olan bibliyografik künye karekodu oluşturma etkinliğine katılanöğrencilerin, öğretmenlerin ve okul kütüphanecisinin etkinliğe yönelik görüşleriincelenmiştir. Çalışma sonucunda söz konusu etkinliğin öğrencilerin bilgi kaynaklarına vekütüphaneye yönelik bakış açılarını olumlu etkilediği ve öğrencilerin kütüphane ortamındakarekodlardan yararlanabilecekleri faydalı bir etkinlik olduğu ifade edilmiştir.Article Ortaokul Öğrencilerinin Dijital Ayak İzi Farkındalıkları ve Yaşantılarının İncelenmesi(2021) Akkoyunlu, Buket; Soylu, Meryem Yılmaz; Demiröz, SevaBu çalışmanın amacı ortaokul öğrencilerinin dijital ayak izi farkındalığını sınıf düzeyi, cinsiyet, elektronik araç ve ortamlarda geçirilen süreye göre incelemektedir. Öncelikle ortaokul öğrencileri için geliştirilen dijital ayak izi ölçeği psikometrik özellikleri açısından değerlendirilerek geçerli ve güvenilir bir araç olduğu ortaya konmuştur. Daha sonra katılımcıların dijital ayak izi farkındalıkları yukarıda belirtilen değişkenlere göre incelenmiştir. Çalışma grubu 204 kız ve 189 erkek öğrenciden oluşmaktadır. Çalışma kapsamında uygulanan Dijital Ayak İzi Ölçeği’nin yanı sıra öğrencilerin cinsiyet, yaş, sınıf düzeyleri ile cep telefonu, internet, sosyal medya kullanımları ve çevrimiçi oyun oynama süreleri hakkında sorular içeren bir form verilmiştir. Sonuç olarak, Dijital Ayak İzi Ölçeği hem araştırmacılar hem de eğitimci, yönetici ve ebeveynlerin kullanımı için geçerliği ve güvenirliği olan bir araç olduğu ortaya konmuştur.Article Citation - WoS: 3Citation - Scopus: 3N-Phosphorylation of Pyrroles: an Intramolecular Migration Reaction(Pergamon-elsevier Science Ltd, 2018) Unaleroglu, Canan; Tasgin, Dilek IsikA new synthetic method is reported for the N-phosphorylation of pyrroles via intramolecular migration of a phosphonate diester group. The reaction proceeds under mild conditions and produces N-phosphorylated pyrrole derivatives in moderate to good yields. (C) 2018 Elsevier Ltd. All rights reserved.Article Citation - WoS: 12Citation - Scopus: 13Implementing Bring Your Own Device (Byod) Model in Flipped Learning: Advantages and Challenges(Springer, 2020) Gunduz, Abdullah Yasin; Akkoyunlu, Buket; Kibar, Pinar NuhogluFlipped learning is a type of blended learning that reverses traditional conceptions about pre-class and in-class activities. This pedagogical approach offers students the opportunity to exert more control over their learning. However, teachers should monitor whether in-class activities deepen pre-learning. In this paper, we present students' experiences regarding the advantages, challenges and future preferences of using BYOD in flipped learning. According to students, being allowed to use their own devices in classroom activities provided them a more comfortable learning environment. The model increased their productivity because they were familiar with their personal devices. Students reported that the BYOD model made storing and retrieving files easier, which enabled them to continue studying without remembering settings. However, students identified challenges, such as being required to carry heavy devices and dealing with poor classroom infrastructure. A few students decided they would rather not bring their own devices again due to weight, but the others indicated that they would prefer to participate in BYOD-embedded flipped learning in the future.Article Citation - WoS: 4Citation - Scopus: 4Impaired Redox Homeostasis in the Heart Left Ventricles of Aged Rats Experiencing Fast-Developing Severe Hypobaric Hypoxia(Springer, 2019) Agascioglu, Eda; Colak, Ridvan; Demirel, Haydar; Cakatay, UfukDespite its rare occurrence, humans and animals have been prone to getting fast developing severe hypobaric hypoxia. Understanding the redox homeostasis related response of an aging heart to this type of hypoxia are crucially important, since the metabolism of myocardial tissue depends on the redox status of proteins. Rodents can tolerate hypoxic stress better than human subjects. This study was aimed at investigating the effects of fast developing severe hypobaric hypoxia on redox status biomarkers; such as, advanced oxidation protein products (AOPP), lipid hydroperoxides (LHPs), protein carbonyl groups (PCO), protein thiol groups (P-SH), and total thiol groups (T-SH) on the myocardial left ventricles of young and aged Wistar rats. The rats were gradually ascended and exposed to an 8000-meter hypobaric hypoxia. While AOPP levels showed no difference, the TSH and PSH concentrations decreased, and the PCO and LHP increased in both of the hypoxic groups than the controls. The TSH and PSH were lower, and AOPP, PCO and LHP were found to be higher in the elderly hypoxic groups than in the young ones. The significant outcome of the study represents that an 8000-meter hypobaric hypoxia could be considered as a severe hypoxic stress, but not life-treating for the rats and would affect both the young and aged left ventricles similarly in respect to impaired redox status. However, if the percentage increases are taken into consideration, it seems that the higher rate of protein oxidation occurs in young hearts; meanwhile aged hearts are more prone to T-SH oxidation.
